Multiple Endocrine Neoplasia (MEN) I is a hereditary disorder in which one or more of the following glands develop excess normal tissue (hyperplasia) or adenoma (tumor): the parathyroid, the pancreas, the pituitary, and (rarely) the adrenals and thyroid gland.

These are all endocrine glands, which produce and secrete hormones into the blood or lymph systems.

The cause of MEN I is genetic. Tumors of various glands appear in the same person, but not necessarily at the same time. The disorder is inherited, may occur at any age, and affects men and women equally.

Most people affected with this syndrome seek medical treatment because of one of the following: peptic ulcer disease, symptoms related to low blood sugar, symptoms related to high serum calcium levels or kidney stones, or symptoms related to pituitary problems (such as headache).

Risk factors are a family history of this disorder, a previous pituitary tumor, and a history of Zollinger-Ellison syndrome.

Symptoms vary greatly from person to person and may be related to peptic ulcer disease, hypoglycemia, hypercalcemia, or pituitary dysfunction.

• Abdominal pain
• Burning, aching, or hunger discomfort in the upper abdomen or lower chest that is relieved by antacids, milk, or food
• Black, tarry stools
• Nausea and vomiting
• Bloated feeling after meals
• Weakness
• Headache
• Vision problems
• Loss of coordination
• Anxiety
• Mental changes or confusion
• Coma if hypoglycemia is untreated
• Loss of appetite
• Muscle pain
• Fatigue
• Sensitivity to the cold
• Unintentional weight loss
• Low blood pressure
• Loss of axillary or pubic hair
• In women, cessation of menses, infertility, or failure to lactate
• In men, decreased sexual interest, loss of body or facial hair

Diagnostic tests are used to evaluate the function of each endocrine gland.

Pancreatic evaluation may reveal the following signs:

• MRI of abdomen shows a pancreatic tumor.
• CT of abdomen shows a pancreatic tumor.
• Insulin test may show increased levels.
• Fasting blood sugar may be low.
• Serum glucagon may be elevated.
• Serum gastrin may be elevated.

• Serum calcium level is elevated, and the serum parathyroid hormone is increased.
• Parathyroid biopsy shows tumor or hyperplasia

• Cranial CT scan or MRI of head may reveal a pituitary tumor.

• Serum thyroid stimulating hormone (rarely used)
• Cortisol
• Serum adrenocorticotropic hormone
• Serum luteinizing hormone
• Serum follicle stimulating hormone

Surgical removal of the affected gland is the treatment of choice, although therapy with a medication called bromocriptine may also be used for pituitary tumors that secrete prolactin. Hormonal replacement therapy is indicated when glands are removed or secretion is inadequate.

Pituitary and parathyroid tumors are usually benign, but some tumors may become malignant (cancerous), accounting for overall decreased life expectancy. The symptoms of peptic ulcer disease, hypoglycemia, hypercalcemia, or pituitary dysfunction should respond to treatment.

Recurrent tumors may develop.

Call your health care provider you notice symptoms of MEN I.

Screening of close relatives of people affected with this disorder is recommended.